Camera set / scene setup
This sounds quite ridiculous, but your scene might actually be upside-down. If this is the case, just select all your objects, and rotate them 180 degrees on the Y axis. You can also rotate your camera to be upside-down the same way if your scene is to large to be entirely rotated. If the scene is not the problem, look at the camera settings. The view might be distorted, or the camera you are moving may not be the active camera.